Generally, in silver halide photographic light-sensitive materials, it is desirable to increase iodide content for the purpose of high sensitization, etc.
For example, in conventional medical X-ray films, silver iodobromide emulsions containing, generally, about 2 mol % iodide are frequently used without carrying out spectral sensitization. However, if the iodide content of the emulsion can be increased, higher sensitization should be able to be achieved, because the absorptivity of blue light increases, and higher sensitization has actually been achieved in this manner. Higher sensitization can be utilized for increasing optical density (the so-called covering power) of developed silver by making fine grains. Further, in a film wherein light-sensitive emulsions are applied to both sides of a base, the undesirable so-called cross-over light effect (whereby not only the emulsion face in contact with each layer of fluorescent substance but also the other emulsion face on the reverse side of the base is exposed to blue light emitted from the fluorescent intensifying screen by X-rays) can be reduced by increasing the iodide content of the emulsion, with higher sharpness thereby being attained. In addition, it is very desirable to increase the iodide content in order to provide a sufficient effect of the type described in Japanese Patent Publication 2068/66, U.S. Pat. Nos. 2,996,382 and 3,178,282, Japanese Patent Publications 27065/69 and 8738/72 and U.S. Pat. No. 1,426,277, namely, the effect of increasing the covering power of developed silver by developing fine internally fogged grains with iodine released from light-sensitive grains during development.
Although increasing the iodide content has numberous advantages, there are also some serious problems absociated therewith. For example, the high iodide content emulsions have a serious problem in that the photographic properties (e.g., sensitivity, gradation, and fog) are greatly influenced by factors such as the processing temperature and the amount of halogen in the processing solution when they are processed with a high temperature rapid developing solution containing a glutaraldehyde type hardener. In order to reduce the processing condition reliance (temperature, amount of halogen, and the like) of photographic properties in the high temperature developing solution, certain techniques have been known. For example, such techniques include an effect of preventing yellow fog by addition of nitron salts (e.g., 1,4-diphenyl-3,5-eudsanilin-4,5-dihydro-1,2,4-triazole, 3,5,6-triphenyl-2, 3,5,6-triphenyl-2,3,5,6-tetrazabicycles (2,1,1) hex-le as described in Japanese Patent Publication 28691/77, and Research Disclosure (RD)-18431, page 434; and effect of improving processing temperature reliance by addition of meso-ionic triazolium compounds other than nitron, as described in Japanese Patent Application Nos. 196560/83 (corresponding to U.S. patent application Ser. No. 662,112 filed on Oct. 12, 1984), 224762/83 and 231088/83 (corresponding to U.S. patent application Ser. No. 678,906 filed on Dec. 6, 1984), an effect of preventing fog by means of mercapto compounds and benzotriazole compounds described in U.S. Pat. Nos. 3,954,474 and 3,982,947 and Japanese Patent Publication No. 28660/77, an effect of improving processing temperature reliance by addition of nonionic surface active agents having one polyoxyethylene chain in the molecule described in British Pat. No. 861,134 and West German Pat. No. 1,422,809; an effect of preventing fog in color developing solutions by means of blue-light spectrally sensitizing dyes as described in U.S. Pat. No. 2,131,038, Japanese Patent Application (OPI) No. 61519/79 (the term "OPI" as used herein means a "published unexamined Japanese Patent Application"), U.S. Pat. No. 3,930,860 and Japanese Patent Application (OPI) No. 119917/75; and improvement (viz., a decrease) in processing temperature reliance by means of selective blue-light spectrally sensitizing dyes, though such technique is restricted to tabular grains, as described in Japanese Patent Application Nos. 166321/82 (corresponding to U.S. patent application Ser. No. 536,044 filed on Sept. 25, 1984) and 40249/83 (corresponding to U.S. patent application Ser. No. 588,410 filed on Mar. 12, 1984). However, these techniques have problems of desensitization, fog, etc.
For example, meso-ionic triazolium compounds show a great desensitization effect, though having an effect of improving processing reliance and a desensitization effect (particularly, the desensitizaction effect in a developing solution containing no glutaraldehyde is very great). Mercapto compounds show a very great desensitization effect as compared with their beneficial effect of improving processing reliance. Light-sensitive materials containing polyoxyethylene compounds as described in Japanese Patent Application (OPI) No. 185304/83 have probelms in that they easily form pressure mark caused by rollers used in the automatic developing apparatus, and the granularity easily deteriorates in a developing solution containing no glutaraldehyde.